Standard Metal Stock Items

Steel square tubing

Welding involves base metal that comes in many shapes, sizes and tensile strengths. Entry-level welders should be familiar with the standard stock items sold by steel and pipe distributors, since this is the material they'll be welding on. MetalsDepot.com publishes a free catalog(PDF) which lists the most common stock items. Below you'll find an overview of materials used in welding and fabrication shops:

Flat Bar

This inexpensive hot-rolled, solid steel is a familiar item in welding schools, where it's cut into small pieces and used as practice work plates. In manufacturing and construction, flat bar is used for used for rails, braces, brackets and frames.

Round Bar

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This solid metal bar is used for stakes, grates, frames and fencing.

Angle

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An extremely common construction material, angle steel is used for fabrication where the stronger tubing isn't needed. It's also cut up to make brackets or used for framing, crossmembers and brick lintels.

Channel

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Another common building material, hot-rolled steel channel is used for racks, trailers, cross-members and framing.

Square Tubing

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Metal tables and work benches that need to be sturdy are usually built from square tubing, also referred to as HSS. The tubing is hollow but not meant to carry liquid, so the inside measurment of the hole is of no importance. The thickness of the "wall", however, is included in the product specification. A typical size of square tubing is one inch, with a .065 wall. As you can see, both American and metric systems are used for the same item. Tubing is available in different metal types (aluminum, stainless steel, etc.). Most steel framing uses cold-rolled steel, but many shop fabricators use hot-rolled steel as well.

Round Tubing

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For ergonomic or practical reasons, some frames need to be round. Hollow tubing is obviously a lot lighter than solid bar and therfore cheaper to buy. Round tubing is specified by outside diameter and wall size.

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Rectangular Tubing

Like square tubing, the rectangular version is used to build sturdy tables and work benches, as well as warehouse supply bins and racks.

Expanded Metal Mesh

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Why waste a heavy sheet of steel when "expanded" metal will do the trick? Decking, fence, cages and bins are made from this product, which allows you to see through it as well.

Sheet and Plate

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As a rule, flat metal with a wide face compared to its thickness is classified as sheet or plate. (Flat bar, by contrast is long and not very wide.) If the thickness is below a quarter inch, the metal is considered sheet and measured in gauges. (A 16-gauge sheet, for example, is 1/16 inch thick.) Metals that are thicker than 1/4 inch are classified as plate and measured in fractions or millimeters. Sheet and plate are used for box construction, table tops, air ducts, vehicle and airplane bodies, and many consumer products.

Tool Steels

As the name implies, tool steels are used to make tools - drills, taps, dies, arbors, shafts, machinery parts, pins, punches, roller bearings, etc. A much higher carbon content and density is needed, since tools may be subjected to powerful forces repeatedly (especially when cutting or drilling). When manufactured, the metal gets a special heat treatment to make it harder. The downside is that the steel may become more brittle, so you don't want to be carelessly dropping tool grades of metal, labeled in the ASTM range of "A2" to "A10", on hard surfaces.